by MIM Damanhuri · 2016 · Cited by 51 — schools achieved the intended curriculum on acid-base concepts. about acids and bases that are held by students and teachers alike (Chiu, 2004, 2007;.
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International Journal of Environmental & Science Education , 201 6 , 1 1 ( 1 ), 9 – 27 6 by iS ER , International Society of Educational Research ISSN: 1306 – 3065 Understanding of Acid – Base Concepts: An Ongoing Challenge for Teachers Muhd Ibrahim Muhamad Damanhuri Sultan Idris University of Education , MALAYSIA David F. Treagust Curtin University , AUSTRALIA Mihye Won Curtin University , AUSTRALIA A. L. Chandrasegaran Curtin University , AUSTRALIA Received 04 June 201 5 Revised 1 0 Jul y 201 5 Accepted 07 September 201 5 Using a quantitative case study design, the Acids – Bases Chemistry Achievement Test ( ABCAT ) was developed to evaluate the extent to which students in Malaysian secondary schools achieved the intended curriculum on acid – base concepts. Responses were obtained from 260 Form 5 (Grade 11) students from five schools to initially create the two – tier multiple – choice items. After pilot testing, the final version of the ABCAT consisting of 19 items, 10 multiple – choice items and nine two – tier mu ltiple – choice items, was administered to 304 students in Form 4 (Grade 10) from seven secondary schools when 12 alternative conceptions were identified by at least 10% of the students. Of these alternative conceptions, three were displayed by less than 15% of students. The two – tier multiple – alpha) of 0.54 than the multiple – choices items with a value of 0.42. The data from the study suggest that the ABCAT has shown the extent to which the teaching has reduced the the 19 items, no alternative conceptions were displayed by the students. Keywords : a cid – base concepts; diagnostic assessments; multiple – choice and two – tier multiple – choice items INTRODUCTION The topic on acids and bases has posed many problems to students of various backgrounds. From as early as several decades ago the topic on acids and bases has been reported to be difficult for high school students (Bur ns, 1982) who have as a result held several alternative conceptions about acids and bases (Artdej et al., 2010; Correspondence : Muhd Ibrahim Muhamad Damanhuri , Jabatan Kimia, Fakulti Sains dan Matematik , Universiti Pendidikan Sultan Idris , 35900 Tanjong Malim , MALAYSIA E – mail: muhdibrahim@fsmt.upsi.edu.my doi: 10.12973/ ijese.2015.284 a
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M . I. M. Damanhuri , D. F. Treagust, M. Won & A. L . Chandrasegaran 10 6 iS ER , International J. Sci. Env. Ed. , 1 1 ( 1 ), 9 – 27 Cros et al., 1986; Hand & Treagust, 1991 ; Nakhleh & Krajick , 1993). Even until recently, several studies have been documented that refer to alternative conceptions about acids and bases that are held by students and teachers alike (Chiu, 2004, 2007; Ayas, 2013; difficulties in understanding acid – base concepts date back several decades, in this paper we have decided to refer to studies that have identified several alter native conceptions about acids and bases among students and teachers that were conducted during this century . The purpose of this study was to develop a diagnostic test based on the approved chemistry curriculum, referred to as the Acids – Bases Chemistry Ac hievement Test ( ABCAT ), to evaluate the extent to which students in a sample of Malaysian secondary schools had achieved the intended curriculum on acid – base concepts following a regular program of instruction. THEORETICAL BACKGROUND According to the cons tructivist view of learning, what a learner already knows is a major factor that determines the outcomes of learning (Ausubel, 1968). Students develop their views about scientific concepts and phenomena based on their sensory experiences, cultural backgrou nds, peers, mass media as well as classroom instruction (Chandrasegaran, Treagust & Mocerino, 2008) . There is a tendency for students to be satisfied with their own conceptions because they are often deeply rooted and supported in their daily life experien ces (Chandrasegaran, Treagust & Mocerino, 2008) . could differ from scientifically acceptable conceptions and may cause learning difficulty, especially when the new science concepts are not al igned with their prior experience or conceptual framework. When the new science concepts do not make sense to them, students tend to adhere firmly to their own private views. science concepts so that appropriate instructional strategies may be formulated to (Chandrasegaran, Treagust & Mocerino, 2008) . Understanding of strong and weak acids and alkalis Sever al studies have shown that understanding the nature of acids and bases can be confusing. In a study by Chiu (2004), 13% of junior and senior high school students and 34% of senior high school students considered weak electrolytes as consisting of molecules but changed into ions when an electric current was passed through the electrolytes. About 25% of junior high school students also believed that when solutions of equal concentrations of a weak acid like ethanoic acid (CH 3 COOH) and a strong alkali like sod ium hydroxide (NaOH) were mixed, the resulting solution was neutral because the two substances had reacted completely with each other. She also found that 19% of junior and 9% of senior high school students believed that a weak electrolyte exists as molecu some molecules decompose to ions, then positive and negative ions attract with each (p. 435). With elementary school students in Taiwan, Huang (2004) found that 44% of students assumed that soapsuds were neutral because they were not harmful to human skin or to clothes, while 36% thought that a mixture of a solution of sodium bicarbonate and ethanoic acid was neutral because they produced a neutralisation reaction when mixed together. At the same time, 27% of students assumed that all acids and bases were toxic.
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– base concepts 6 iS ER , International J. Sci. Env. Ed. , 1 1 ( 1 ), 9 – 27 11 Understanding of pH values – Observe – tone, 1992) in a fourth activity Sheppard (2006) investigated the understanding about acid – base concepts among 16 American students who were in grades 10 or 11 (16 – 17 year – olds). Only four students were able to provide the correct formula for pH as pH = – log [H + ], while the rest of the students (N = 12) assumed that pH was a linear scale. However, only one of these four students was able to explain the difference between pH 3 and 5 as representing a hundred fold difference in the H + ion concentration. At t he same time, 14 students assumed that all indicators changed colour at the same pH value of 7. Six students assumed that the process of neutralization involved the physical mixing of an acid and a base while 10 students were aware that a chemical reaction was involved. The products of a neutralization reaction were considered to be acidic by two students and neutral by 13 students. In the conductimetric titration in activity 4 involving addition of a strong alkali to a fixed volume of strong acid, all the students predicted that the pH would progressively decrease, the reason being alkalis have high pH values and acids have low ones. Only two students predicted an S – shaped curve while eight students suggested a linear representation of the change in pH as a cid was progressively added to a fixed volume of alkali. Only one of these two students was able to provide the correct explanation; the other recalled the shape from reading in the textbook but was unable to explain why. After performing the titration, se veral alternative conceptions horizontal, seven students suggested that the reaction had not started as yet, while four students believed that no reaction was occurring. Onl y three students believed that the acid and alkali were actually reacting in the initial part of the titration. The sudden change in pH in the second part of the curve was attributed to reaction suddenly occurring by five students. The correct explanation was provide d by only three students who suggested that the acid and alkali were of approximately equal concentrations, so that when more acid was added a large change in [H + ] ion concentration would occur and hence in pH. The levelling of the pH in the thi rd section was attributed by half the number of students to the presence of an excess of acid particles resulting from a mixing of the acid and alkali, not because of any chemical reaction occurring. Only three students explained that there was an increase in the concentration of H + ions as a result of the reaction involving the removal of all the OH pH and chemical change compared to the other tasks probably because they were making spontaneous attempts to explain what to them appeared to be a discrepant event. Understanding of other acid – base concepts In another study using POE activities and interviews with 27 high school students, Kala, Yaman and Ayas (2013) investiga ted their understandings of acids and bases. Some of the students were found to have alternative conceptions about pH and pOH. In one of the POE tasks the students were required to predict the pH and pOH sequence for substances like tap water, lemon juice and HCl. The expected sequence of pH tap water < pH lemon juice < pH HCl , with the reverse order for pOH was provided by 21 of the students, but only one student gave the correct explanation for the reason for the sequence. At the same time, only four studen ts provided partially correct reasons for the prediction. In conclusion, most students believed that pH was associated with acids and pOH with alkalis.
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M . I. M. Damanhuri , D. F. Treagust, M. Won & A. L . Chandrasegaran 12 6 iS ER , International J. Sci. Env. Ed. , 1 1 ( 1 ), 9 - 27 (2005) used a conceptual conflict instructional strategy to remediate alternative conceptions that were held by 88 grade 10 students (aged 16 - 17 years) from a high school in Turkey. They used a pretest - posttest control group - experimental group design, wit h the two groups involving two classes each that were taught by two different teachers. Part of the study involved using a Concept Achievement Test ( CAT ) consisting of 20 multiple - choice items on acid - base concepts that was administered before and after in struction. During instruction of the students in the experimental group, the teacher attempted to help the students to recognise and resolve the conflict between their own knowledge and scientific knowledge using worksheets, analogies and practical work. T he control group students, on the other hand, were instructed in a traditional manner involving chalk - and - talk and some practical work. There was no significant difference in the pretest mean scores of the two groups indicating that the students in the two groups were equivalent. However, when the mean posttest scores of the two groups were compared after instruction using an independent samples t - test, there was a significant difference in the scores with the students in the experimental group achieving hi gher mean scores [(experimental group: M = 73.9, SD = 12.7); (control group: M = 60.0, SD = 15.9); t = 4.50, p < 0.001]. Before instruction, the percentage of misconceptions held by students in the experimental group ranged from 18% to 84%, while that in t he control group it ranged from 20% to 95%. After instruction, this percentage ranged from 0% to 23% for the experimental group and from 2% to 43% for the control group. Multiple - topic. However, they are not without limitations. Multiple - choice items often involve a limited number of short answer options without elaboration of the reasons. To address the limitations of multiple - choice items, Tamir (1990) incorporated known alternative conceptions in the responses and required students to provide a reason for selecting a particular response. The provision of justifications to address the limitation of mult iple - choice items, proved to be more sensitive and effective in - tier multiple - choice items by Treagust (1988, 1995) that enabled the identification of onceptions in specific content areas. The first tier is a content question followed by a number of multiple - choice options. The second tier provides a number of alternative justifications for the choice of the answer to the first tier. These short pencil a nd paper tests are convenient to administer and it does not take long to mark manually. For large samples, specially designed answer sheets can be marked efficiently using optical marking machines that electronically read the answers and summarise the resp onses in a data file for subsequent analysis. Treagust (1988, 1995) has provided useful guidelines for the development of instruments containing two - tier multiple - choice items. Figure 1 provides a sample scheme for this development (Treagust & Chandrasegar an, 2007) . The development of two - tier multiple - choice diagnostic instruments has been reported in the science education research literature since the 1980s, involving a variety of concepts (Treagust & Chandrasegaran, 2007) . One of the earliest two - tier in struments involved the concepts of photosynthesis and respiration in green plants (Haslam & Treagust, 1987) . Several other instruments have been developed over the past three decades or so concerning topics and concepts like diffusion and osmosis (Odom and Barrow 1995), chemical equilibrium (Tyson, Treagust & Bucat, 1999) , chemical bonding (Tan & Treagust, 1999) , multiple representations in chemical reactions (Chandrasegaran, Treagust & Mocerino, 2007) , ionisation energies of elements (Tan, Taber, Goh and Chia 2005), electrolysis (Sia, Treagust & Chandrasegaran, 2012) and electrochemistry (Rahayu, Treagust, Chandrasegaran, Kita & Ibnu, 2011) , to name a few.
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- base concepts 6 iS ER , International J. Sci. Env. Ed. , 1 1 ( 1 ), 9 - 27 13 Figure 1 . Stages in the development of two - tier multiple - choice diagnostic instruments based on the methodology proposed by Author (1988, 1995) Although several two - tier items on acids and bases have been previously f science concepts (Chiu, 2007), the items were not appropriate for the contents of the Malaysian secondary chemistry syllabus because the chemistry curricula on acids and bases of the two countries were found to be different. For a similar reason, a two - t ier Identify major scientific concepts Identify propositional knowledge statements Develop concept maps Examine related literature explanations using free response exercises explanations using multiple - choice content items with free response justifications Conduct semi - structured interviews Develop first draft instrument Develop second draft instrument Develop final instrument Stage 1: Define content Stage 2: Obtain informa tion about conceptions Refine instrument Design specification grid Stage 3: Develop 2 - tier diagnostic instrument
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M . I. M. Damanhuri , D. F. Treagust, M. Won & A. L . Chandrasegaran 14 6 iS ER , International J. Sci. Env. Ed. , 1 1 ( 1 ), 9 - 27 instrument used in a Thai study involving grade 11 students (Artdej et al., 2010) was not applicable for this study to evaluate the basic acid - base concepts. Hence, an alternative two - tier multiple - choice instrument on acids and bases, the Acids - Base s Chemistry Achievement Test (ABCAT) , was developed for this study. When ordering statements about what we expect students to learn, we often make , 2010). These objectives are organised in a hierarchical order that progressively become more These are knowledge, comprehension, application, analysis, synthesis and evalua tion. This order of complexity can also be taken into account when developing assessment items. Rationale for the study Concepts of acids and bases continue to be a problem for students at all levels of schooling as indicated by several past studies (e.g . Chiu, 2004; Huang, 2004: Kala, Yaman & Ayas, 2013; Sheppard, 2006). This study was conducted to evaluate the learning of high school students following a program of regular instruction using an instrument consistin g of items that targeted several commonly held alternative conceptions. The absence of some of these alternative conceptions in this study following instruction contributes to the current literature by making available an alternative and efficient diagnost ic instrument. Objectives of the study The Acids - Bases Chemistry Achievement Test ( ABCAT ) was developed in order to of acid - base concepts. The ABCAT has three major characte ristics. First, it is a achieving the intended outcomes of instruction (Bell & Cowie, 2001) on acids and bases. Second, the ABCAT is a standardized type of test where studen ts from all the participating schools respond to the same set of test items under similar conditions (Anderson, 2003). Third, the ABCAT consists of multiple - choice items that offer a fast uthor, 2006), enabling the teacher to give coherent judgements on their understanding by each student. Consequently, the main research question that guided this study was to determine the extent to which the ABCAT could identify the incidence of acid - base alternative conceptions among Grade 10 students following a program of regular instruction. METHODOLOGY The study employed a quantitative research design (Cohen, Manion & Morrison, 2011) that involved the development and administration of the ABCAT. Develo pment and administration of the ABCAT Development of test items From the Malaysian Forms 4 & 5 (Grades 10 & 11) Chemistry Curriculum Specifications, we have identified a total of 21 out of 26 learning outcomes that describe the Acids and Bases topic, as summarised in Figure 2. These learning outcomes were categorised into four major concepts, namely (1) charact eristics and properties of acids and bases, (2) strengths of acids and alkalis, (3) concentration of
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M . I. M. Damanhuri , D. F. Treagust, M. Won & A. L . Chandrasegaran 16 6 iS ER , International J. Sci. Env. Ed. , 1 1 ( 1 ), 9 - 27 lecturer. Meanwhile, the bilingual items had been assessed in terms of face validity through back - translation technique (Brislin, 1970). A specification grid (see Figure 3) was drawn up relati ng the 22 items in the ABCAT to the 21 learning outcomes that were previously identified in Figure 2. Instrument psychometrics The difficulty and discriminatory indices for each of the 22 items are summarised in Table 1. Items with difficulty indices in the ranges 0.00 0.20, 0.21 0.80, and 0.81 1.00 are considered difficult, moderate and easy, respectively (Popham, 1995). Based on these criteria, nine of the 12 items in Section A were moderately difficult, while the remaining three items were consid ered to be easy. As for the items in Section B, eight of the 10 items were moderately difficult while one item was easy and one item was difficult. The wide range in the difficulty indices catered for students with varying abilities (Taylor & Nolan, 2005). Regarding the discrimination indices, values for items in Section A ranged from 0.00 to 0.50, while the values for Section B ranged from 0.11 to 0.70. According to Authors (2008) items with discrimination indices below 0.2 may not discriminate well between students. Three items, A2, A6 and B3, which had discrimination indices below the threshold value of 0.2 were deleted from the ABCAT leaving 10 items in Section A and nine items in Section B. The final version of the ABCAT containing 19 items (10 multiple - choice items in Section A and nine two - for Sections A and B of 0.42 and 0.54, respectively. The importance of conceptual tests like the ABCAT is attributed to the convenience in administerin g the test by minimising the time required to complete a limited number of items. In such e as it may indicate the presence of redundant items that need to be deleted (Adams & Wieman, 2011). The final version of the ABCAT containing 19 items (10 multiple - choice items in Section A and nine two - tier items in Section B) is found in the Appendix. Research participants Table 1. Difficulty and discriminatory indices of the 22 items in the ABCAT Difficulty & discriminatory indices Section A items (12 items) Section B item (10 items) Difficulty index range 0.11 0.20 B3 0.21 0.80 A3; A4; A5; A7; A8; A9; A10; A11; A12 B1; B2; B4; B5; B6; B8; B9; B10 0.81 1.00 A1; A2; A6 B7 Discrimination index range 0.00 - 0.20 A2; A6 B3 0.21 0.30 A1; A4; A8 B7 0.31 0.40 A3; A5; A9; A11 B6; B8 0.41 - 0.50 A7; A10; A12 B10 0.51 0.70 B1; B2; B4; B9; B5
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- base concepts 6 iS ER , International J. Sci. Env. Ed. , 1 1 ( 1 ), 9 - 27 17 The final version of the ABCAT was administered to 304 Form 4 students from seven schools in the district of Melaka Tengah, Melaka in 2011. Students were given 45 minutes to answer the questions. RESULTS Comparison of pretest and posttest performances in the ABCAT - base concepts in the pretest and posttest using the ABCAT . An independent samples t - test analysis showed that the scores for the posttest were significantly higher than that for the pretest for both sections as well as for the overall instrument (see Table 2). The strength of the difference between the pretest and posttest mean scores may d . Cohen (1988) has defined the effect size as being small when d = 0.2, medium when d = 0.5 and large when d = 0.8. d values suggest that the difference b etween the Section A means was average, that between Section B means was close to large while the mean differences between the overall mean scores were very large. Table 2. Comparing the ABCAT test scores (N = 304) Section Pretest Posttest t - value Effect size d ) Mean SD Mean SD Section A 3.69 1.82 6.00 1.86 **17.40 0.42 Section B 2.69 1.62 3.94 1.93 **9.72 0.70 Total 6.39 2.83 11.94 3.28 **25.66 1.81 ** p < 0.01 (Note: Section A consists of 10 multiple - choice items; Section B consists of nine two - tier multiple - choice items). Table 3 . Comparison of percentage of students who provided correct responses to each of the items in the ABCAT in the pretest and the posttest (N = 304) Item No. Correct response Pretest Posttest A1. A 42.8 87.8 A2. A 32.9 38.2 A3. B 31.9 50.3 A4. B 44.1 71.1 A5. B 29.3 49.7 A6. D 17.8 48.4 A7. B 60.9 80.3 A8. D 25.7 59.2 A9. C 41.8 44.7 A10. C 42.4 70.1 B1. D2 10.5 33.9 B2. C2 28.9 46.1 B3. A3 19.1 37.8 B4. B1 16.8 42.8 B5. A3 32.9 48.7 B6. A1 75.3 88.5 B7. A3 32.9 30.3 B8. C1 33.6 40.8 B9. B1 19.4 25.0 (Note: A1 A10 are Section A multiple - choice items; B1 B9 are Section B two - tier multiple - choice items)
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M . I. M. Damanhuri , D. F. Treagust, M. Won & A. L . Chandrasegaran 18 6 iS ER , International J. Sci. Env. Ed. , 1 1 ( 1 ), 9 - 27 The changes in the understandings of acid - base concepts as a result of the instruction are evident for each of the items in the final version of the ABCAT in the data provided in Table 3. There was an improvement in the posttest scores over that of the pretest scores for all items except Item B7. Alternative conceptions displayed by students Further analyses were performed to identify the alternative conceptions about acid - base concepts that were still held by the students after instruction. An arbitrary ensu re that certain alternative conceptions were not excluded. The students were found to display a total of 12 alternative conceptions that are summarised in Table 4. Table 4. Summary of alternative conceptions about acid - base concepts held by the students (N = 304) Item no. Response option Percentage Alternative conceptions A9 A 16.7 When a standard solution of specific concentration is diluted, the concentration of the solution will increase, while the number of moles of solute present will decrease. A9 B 13.5 When a standard solution of specific concentration is diluted, the concentration of the solution will increase, while the number of moles of solute present will remain constant. A9 D 25.0 When a standard solution of specific concentration is diluted, the concentration of the solution will decrease, while the number of moles of solute present will also decrease. A10 B 17.1 Aqueous potassium hydroxide reacts with aqueous sodium chloride to produce a salt and water. B1 B2 16.8 Sodium hydroxide dissolved in propane ionises to produce OH - ions. B2 C1 11.8 A solution with a pH of 3 contains a higher concentration of OH - ions than H + ions. B3 C3 16.8 A measuring cylinder is the main apparatus that is used in the preparation of a standard solution because it can measure a fixed volume of solution accurately. B4 A3 27.6 Both sulfuric acid and ethanoic acid are strong acids because they ionise completely in water to produce H + ions. B5 B2 16.8 HCl and CH 4 are both acidic because they contain H atoms in their molecular formulas. B7 A1 43.8 Soaps and detergents as well as household cleaners contain alkaline chemicals that are able to wash away stains because alkalis are soapy. B8 C2 11.2 Slightly acidic soil promotes the growth of grass. So, lime is added to change the pH of soil to a value greater than 7. B9 A2 28.9 Aqueous solutions of potassium hydroxide as well as ammonia are both weak alkalis because they are only partially ionised in water.
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- base concepts 6 iS ER , International J. Sci. Env. Ed. , 1 1 ( 1 ), 9 - 27 19 DISCUSSION AND CONCLUSIONS This study has shown that there was a significant difference be of acid - base concepts is reflected in the 12 general alternative conceptions displayed by the students; however, three of these were displayed by less than 15% of students. Also, in the posttest alternative conceptions were not displayed in the first eight items of the test in Section A (A1 to A8) and in Item B6, supporting the efficacy of the ABCAT in identifying the incidence of alternative conception s among the students. There was generally an improvement in the posttest scores for all except one item. In particular, students displayed limited understanding regarding (1) the properties of alkalis (Item B1), (2) the use of a volumetric flask for prepar ing a standard solution (Item B3), (3) the function of soaps and detergents as cleaning agents (Item B7), (4) the treating of acidic soils (Item B8), and (5) the difference between strong and weak alkalis (Item B9). Yet, more than 80% of the students were (1) aware that acids ionise in water to produce H + ions, (2) aware that the pH of a neutral solution was equal to 7, (3) able to demonstrate the correct sequence in the preparation of a standard solution, (4) able to write the chemical equation for the rea ction between an acid and a base, and (5) aware that citrus fruits are acidic with a pH value of less than 7, further supporting the usefulness of the ABCAT in identifying the incidence of alternative conceptions. The improvement in the posttest mean score s also indicates effectiveness to some degree of the instruction, similar to the study conducted by he ABCAT - base concepts; nevertheless, many of these students still held some alternative conceptions about acids and bases . The confusion about the properties of acids and bases that were identified in this study is not surprising as other studies that have been conducted in different cultures as in Taiwan by Chiu (2004) and Huang (2004), in the US by Sheppard (2006) and in T urkey by Kala, Yaman and Ayas (2013) have all indicated related confusion. - base concepts has been and reduced fol lowing regular instruction that was based on the expected learning outcomes stipulated by the Curriculum Development Division (CDD) of the Malaysian Ministry of Education. The findings show that there is still a need for these Malaysian science teachers to carefully review their classroom instruction to ensure that students are provided with opportunities to develop appropriate understandings of acid - base concepts. One recommended solution to address this situation would be for the CDD to prepare lists of propositional content knowledge statements for each topic in the syllabus for distribution to schools so that teachers have a thorough understanding of the relevant concepts. Their instruction could then be organised around these propositional content know ledge statements. At the same time, teachers need to be aware of relevant formative assessment procedures and to institute appropriate remedial measures during the course of their instruction. Due to the large number of schools and science teachers in the country, professional development workshops on formative assessment procedures for key personnel could be considered. Using the multiplier effect, these key personnel could then transmit what they have learned to senior science teachers at district level who in turn could conduct workshops for science teachers in their own schools. The results of this study could be used by chemistry teachers to extend their
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